1. Field of the Invention
This invention relates to an elastro-plastic damper for absorbing vibration energy which a structure such as a building and facilities possibly receives from earthquake motions and ground vibrations.
2. Description of the Prior Art
A typical application of elasto-plastic dampers to a structure such as a building and facilities is a vibration isolation mechanism, and various shapes of elasto-plastic dampers have hitherto been proposed. Generally, this vibration isolation mechanism comprises multi-layer rubber supports, and dampers, etc. which are disposed between the foundation and the upper structure of the building in order to reduce vibrations of the upper structure which are possibly created by earthquake motions and other ambient vibrations. NIKKEI ARCHITECTURE issued Dec. 30, 1985 by Nikkei-McGraw-Hill Inc. discloses various kinds of vibration isolation mechanisms, some of which are still under research. This publication also discloses a variety of types of dampers for vibration isolation mechanism, such as a viscous damper employing a viscous substance (asphalt silicone oil), a cylinder-type oil damper, an elasto-plastic damper employing a soft steel rod, a coil-type elasto-plastic damper, an elasto-plastic damper having a support as a guide for deformation of a steel rod, and a damper having a steel rod built in a multi-layer rubber support.
However, oil dampers and viscous dampers require maintenance and are difficult to design, with which so much high degree of energy absorbability cannot be expected. Particularly, the oil damper has the limited directional property. Also with the prior elasto-plastic dampers using a soft or rigid steel rod, so much high degree of energy absorbability cannot be expected. The prior elasto-plastic dampers are complex in shape, large-sized and difficult to design.